Field of the Invention
The present invention relates to high-power-factor power-line-operated electronic power supplies (ballasts) for gas discharge lamps.
In general, to meet industry requirements, a gas discharge lamp ballast has to draw power from the power line with a power factor of at least 90%. However, with many electronic ballasts, even at a power factor above 90%, the resulting harmonic distortion of the current drawn from the power line may be unacceptably high, particularly with respect to the so-called odd triplet harmonics.
In an electronic ballast--which generally requires a well filtered DC voltage for operating an inverter that powers the gas discharge lamp--by applying unfiltered full-wave-rectified power line voltage to a high frequency inductive-discharge forward converter, such well filtered DC voltage may be attained without incurring any substantial harmonic distortion of the current drawn from the power line. However, the cost penalty associated with providing a forward converter in an electronic ballast is substantial.